Area Forecast Discussion
Issued by NWS St. Louis, MO

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FXUS63 KLSX 240001
AFDLSX

Area Forecast Discussion...Updated Aviation
National Weather Service Saint Louis MO
701 PM CDT Sat Sep 23 2017

.SHORT TERM...  (Through Late Sunday Afternoon)
Issued at 307 PM CDT Sat Sep 23 2017

Early this afternoon, an upper level RIDGE remains dominant over our
region.  Under this RIDGE, a couple "airmass" showers have developed
but have also been very short lived.  A large surface high pressure
is centered over the eastern Great Lakes, a bit further north than
24hrs ago, and has resulted in a more easterly flow over our region
versus southerly like it was yesterday.  This more easterly flow has
resulted in temps a deg or two cooler than 24hrs ago.  A healthy
diurnal cumulus cloud field was over much of our region.  As of this
writing, no record temps have been tied.

Some "airmass" showers or storms could still develop thru sunset,
particularly in northeast, central, or southeast MO.  Otherwise,
look for the diurnal cumulus cloud field to dissipate around sunset
with clear skies overnight.  Persistence will be hard to beat for
min temps overnight, with mid to upper 60s for most areas, and
low 70s for urbanized areas of STL metro.

The upper RIDGE`s influence looks to finally weaken on Sunday as it
moves away further to the east, with the models even showing a weak
upper level disturbance rotating around the RIDGE into southern IL
by Sunday afternoon.  Already have low PoPs going for southeast and
central MO again but this may need to be expanded in coverage in
subsequent forecast packages.

With the departure of the upper RIDGE, max temps should continue to
take more of a hit and edged them down another deg or two from
persistence.

TES

.LONG TERM...  (Sunday Night through Next Saturday)
Issued at 307 PM CDT Sat Sep 23 2017

A very amplified upper air pattern will begin the work week with a
deep trough of low pressure across the Rockies and a strong ridge of
high pressure across the northeast CONUS. Deep south/southwesterly
flow overhead will ensure unseasonably warm temperatures continuing
until the passage of a cold front Tuesday afternoon.

Trof of low pressure attempts to push east by midweek but really
gets shunted to the north into the upper Midwest with the overall
flow becoming more zonal across the center of the CONUS. The
accompanying surface cold front is still expected to move through
the CWA, but with the best dynamics staying well north and limited
low level moisture, PoPs continue to slowly dissapear in the
extended.  At least the front should knock temperatures back to
normal with highs in the 70s.

CVKING
&&

.AVIATION...  (For the 00z TAFs through 00z Sunday Evening)
Issued at 642 PM CDT Sat Sep 23 2017

Clear skies and light east winds to prevail tonight, then will see
scattered diurnal cu develop by midday on Sunday with light
southeast winds.

SPECIFICS FOR KSTL:
Clear skies and light east winds to prevail tonight, then will see
scattered diurnal cu develop by midday on Sunday with light
southeast winds.

Byrd
&&

.CLIMATE...
Record Max Temperatures Through Saturday

              KSTL  KCOU  KUIN
Sept 23     94 (1891)   94 (2007)   95 (1937)
Sept 24     94 (1891)   95 (1891)   94 (1935)


Record High Min Temperatures Through Saturday

              KSTL        KCOU        KUIN
Sept 22     73 (2005)   71 (2005)   71 (1930)
Sept 23     73 (1884)   73 (1937)   73 (1937)


&&

.LSX WATCHES/WARNINGS/ADVISORIES...
MO...None.
IL...None.
&&

$$
WFO LSX


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